Deflection coil and yoke for cathode-ray tubes



March 9, 1948. y R. B. GETHMANN DEFLECTIN COIL AND YOKE FOR CATHODE RAYTUBES Filed oct. 12, 194s Ihverwtov: RiClPd BGetl/wmarww His AttorneyPatented Mar. 9, 17948 DEFLECTION COIL AND YOKE FOR CATHODE-RAY TUBESRichard B. Gethmann, or to General Electri of New York Bridgeport,Conn., assignc Company, a corporation Application October 12, 1946,Serial No. 703,055

9 Claims.

My invention relates to cathode ray tube deilectlng devices of theelectromagnetic type and it has for its primary object to provide a newand improved electromagnetic deflecting coil and yoke.

In receivers for television signals, it is cus tomary to use a cathoderay tube in which the electron beam is modulated in accordance with areceived picture` signal. Means are employed for deilecting the beam toscan the fluorescent end wall of the tube both horizontally andvertically. Such deflecting means are usually either of theelectrostatic or electromagnetic type. One of the problems in the lattertype of deflection system is to maintain as large a percentage aspossible of the magnetic flux established by the windings or coils ofthe deflection device within the neck of the cathode ray tube forcontrol of the electron beam therein. To this end various coreconstructions have been employed. It is an object of my invention toeffect certain improvements in core constructions for an electromagneticdeflecting device for a cathode ray tube.

It is still another object of my invention to provide a new and improvedelectromagnetic deilecting device for a cathode ray tube in which thereluctance of the flux path external to the neck of the cathode ray tubeis large relative to the reluctance of the flux path through the cathoderay tube.

It is a further object of my invention to provide a new and improvedwinding for an electromagnetic deflecting device for a cathode ray tube.

One of the features of my improved electro magnetic yoke consists inconstructing an annular core in which a non-magnetic shield is providedto increase the reluctance of the flux path external to the cathode raytube. The core is surrounded by a toroidal winding having a plurality ofsections of different peripheral length, alternate sections beingconnected to form two circuits deilecting the beam of the cathode raytube in two transverse directions so that the catliode ray beam of thetube may be deflected horizontally' and vertically for scanning purposesin a television receiver.

The novel features which I believe to be characteristic of my inventionare set forth with partieulerity in the appended claims. My inventionitself, both as to its organization and method of operation, togetherwith further objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawings in which Fig. 1 is a longitudinal view of acathoderay (Cl. 25u- 157) tube employing my improved deilecting device;Figs. 2 and 3 are, respectively, vertical and plan views, partly insection, of my beam deflecting device; Fig. 4 is a perspective view of aportion of the core structure of the dellecting device of Fig. 2; andFig. 5 is a circuit diagram of the coils employed in the device of Fig.2.

Referring to Fig. 1, I have shown a cathode ray tube I having a neckportion 2 along which an electron beam is projected toward thefluorescent end wall 3 of the tube. In order to defleet the electronbeam rapidly in horizontal and vertical directions, I provide anelectromagnetic beam deflecting device 4, the exact construction ofwhich is better illustrated in Figs. 2-4.

Referring to Figs. 2-4 jointly, the beam defleeting device 4 comprisesan annular core structure comprising a flat steel wire or ribbon 5 whichis wound into a coil or solenoid with the longer dimension of the ribbonlying in a plane transverse to the longitudinal axis of the wound coil.Preferably, the ferromagnetic metal of which the wire 5 is formed has ahigh permeability so that the wound coil forms a low reluctance fluxpath. The gaps between adjacent of the turns of the wire 5 aresufficient to reduce eddy currents which otherwise would increase thereluctance of the path. In order to increase the reluctance of the fluxpath external to the wires 5 without affectting the reluctance of thepath internal to the solenoid, I provide a non-magnetic conductivesleeve B surrounding the stacked turns of the wire The inner diameter ofthe sleeve 6 is equal to the outer diameter of the turn of the wire 5 sothat the wire lits snugly within the sleeve l. The ferromagnetic coremay be held in position within the sleeve 6 by flaring over the ends l,E of the sleeve.

The core comprising the stacked turns of wires 5 and the copper tube 6is enclosed by a pair oi annular insulators 9, lll located,respectively, on the inner and outer surfaces of the core. Endinsulators H, I2 are provided, respectively, at the upper and lower endsof the core. These insulators may be formed of any suitable moldeddielectric material, such as for example molded cellulose acetate. Asmay best be seen in Fig. e, the insulators 9, I0 are provided With aplurality of spaced notches I3 along their upper and lower edges toreceive and position a corresponding member of C-shaped guides orseparators i4. The vertical portion of the C-shaped guide is adapted tolie on the inner surface of the spacer 9 with the two arms projectingoutwardly and lodging in aligned notches I3 in the edges of theinsulators 9 and IIS. Preferably, the guides I4 are likewise formed of asuitable molded dielectric material, such as cellulose acetate. Disposedbetween the guides I4 are a plurality of coils of wire I 5 tightly woundabout insulators Il, IB, each coil preferably being of the same depthand of varying peripheral length.

The wiring diagram of the coils I5 is shown in Fig. 5. From thisdiagram, it is apparent that adjacent coils I5 are connected indifferent deflecting circuits. The winding which provides horizontaldeflection of the cathode ray beam of the tube is connected between theterminals I5, I'I and includes, on the left-hand side of the .toroidalstructure, the serially connected coils I8-22 and, on the right-handside, serially connected coils 23-21. The output terminal of the coil22, the lowermost of the left-hand coils, is connected to the inputterminal of coil 23, the upper of the right-hand group of coils. Thecoils I8-21 are Vprovided with a different number of turns, the numberin each coil or sector of the winding being adjusted to give asubstantially uniform flux pattern in a horizontal plane. The coils ofthe vertical deflection winding are ccnnected between terminals 28, 29and comprise coils .3Q- 39 connected in series in numerical orderbetween these terminals. The coils of the vertical winding likewise havea different number of turns in different sectors, the sameconsiderations applying in the number of turns thereof on the core,namely, that a substantially uniform flux pattern in a verticaldirection is obtained. In Winding the coils on the core structurepreferably the coils of the vertical winding are wound first. Thereafteran insulator 40 is wrapped around the assembly and the horizontaldeflection coils are wound in position between adjacent of the guides 4In using the deflection devicel described on a cathodeV ray tubeemployed in a television re-l ceiver, the coils of vthe winding whichproduces horizontal deflection are provided with a high frequencysawtooth wave, the frequency being usually of the order of 15,750 cyclesper second. Since, in this type of coil, it is desired to keep theinductance ofthe resultant coil at a minimum, itis desirable to use thesmallest number of turnsper sector cf horizontal coil winding whichgives the desired strength of magnetic field withinthe neck ofthecathode ray tube. I reduce the amount ofmagnetic flux external to thecore structure by utilizing the copper sleeve 6 to increase thereluctance of the external flux path. With this construction the iluxinternal to the coils is increased and the ilux external to the coils isreduced so that a major portion of the magnetic energy is used for beamdeilecting purposes. The vertical deflection coil employed for a cathoderay tube in a television receiver normally is provided with a sawtoothWave having a frequency of the order of 60 cycles. Accordingly, for thecoils of the sectors {iB- 39, the primary consideration is avoiding fluxlinkages with the horizonal deflection windings so that a minimum amountof higher frequency voltage is picked up by the vertical deflectionwindings. At the same time, it is desired that the resistance of thecoil be a minimum so that the power required for deflection purposes iskept as small as possible. This is achieved in my improved coreconstruction by the compact arrangement of core and coils in which aminimum volume of iron is required. By using windings of uniform depth,

the core diameter and air gap are kept to mini mum values.

An important advantage of my improved con-A struction of a deflectiondevice is that the turns of the individual sectors can be adjusted toobtain an optimum sweep pattern by controlling the number of turns ineach sector and adjusting' the width of the sector.

Another important advantage consists in theA improved core constructionby which a maximumK amount of the magnetic ux is confined to a pathinternal to the coils so that a small amount ofv energy is required todeflect the cathode ray beam. By constructing the deilecting device as atoroidal winding, a minimum amount of core material is required and theoverall diameter of the deilection coils and the yoke is kept to arelatively small dimension.

While I have shown and described one particular embodiment of myinvention, it will of course be understood that I do not wish to belimited thereto, since various changes and modications may be madewithout departing from my invention, and I contemplate in the appendedclaims to cover all such changes and modifications as fall within thetrue spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electromagnetic yoke for deflecting the electron beam of a cathoderay tube comprising an annular core comprising a plurality of turns offerromagnetic wire, a non-magnetic conductive sleeve surrounding saidwire, a conductor wound on said core comprising a plurality of adjacentsections, alternate of said sections being connected to form a pair ofcircuits for deflecting the beam of the cathode ray tube in twotransverse directions.

2. An electromagnetic yoke for deflecting the electron beam of a cathoderay tube comprising an annular core comprising a plurality of turns of awire having magnetic properties, a nonmagnetic conductive sleevesurrounding said wire, a conductor wound on said core on the inner andouter surfaces thereof comprising a plurality of turns extendinglongitudinally of said core to form adjacent sections, alternate of saidsections being connected to form a pair of circuits adapted to deflectthe beam of the cathode ray tube in two transverse directions.

3. In a magnetic yoke for deflecting the electron beam of a cathode raytube, a magnetic core comprising a solenoid comprising a plurality ofclosely Wound turns of wire having magnetic properties, a conductivesleeve surrounding said solenoid, and a conductor wound longitudinallyalong the inner and outer surfaces of said core to form a plurality cfcoils of substantially the same depth, adjacent of said coils havingdifferent peripheral length and valternate of said coils being connectedto form a pair of circuits adapted for deflecting the electron beam of acathode ray tube in two perpendicular directions.

4. A winding for producing a uniform field to deflect the electron beamof a cathode ray tube comprising a plurality of coils arranged to form atoroidal winding, :all of said coils being of substantially the samethickness, ladjacent of said coils being of different peripheral length,and alternate of said coils being connected to form a pair of circuitsadapted to establish transverse magnetic elds.

5. A magnetic deecting yoke for producing. a

pair of uniform tnansverse magnetic iields for the deilection of anelectron beam in a cathode ray tube comprising .a solenoid comprising aplurality of turns of wire having magnetic properties, means forincreasing the reluctance of the magnetic flux path of said solenoidalong the outer surface thereof comprising a conductive sleeve disposedalong the outer surface of said solenoid, a conductor wound alternatelyon the inner and outer surfaces of said solenoid land extendinglongitudinally of the axis thereof, means dividing said conductor into aplurality of discrete coils, alternate of said coils being connected toform a pair of continuous windings, one of said windings reversing indirection about the periphery of said solenoid.

6. In a magnetic yoke for deilectin'g the electron beam of a cathode raytube, a magnetic core comprising ia solenoid comprising a plurality ofturns of a fiat Wire having magnetic properties, the major dimension ofsaid wire lying in a plane transverse to the :axis or said solenoid, anonrnagnetic conductive sleeve closely surrounding said solenoid andhaving its end extending inwardly to maintain said turns in closelyspaced relation, and a plurality of coils wound longitudinally along theinner iand outer surfaces of said core, all of said coils being ofsubstantially the same depth and adjacent of said coils having differentperipheral length.

7. An electromagnetic yoke for deflecting the electron beam of a cathoderay tube comprising yan annular core comprising a plurality of turns offerromagnetic wire, a non-magnetic conductive sleeve surrounding saidwire, a plurality of coils wound on said core along the inner and outersurfaces thereof, all of said coils being of substantially the samedepth, insulating means positioned between said coils, and alternate ofsaid coils being connected to form a pair of circuits adapted fordeiiecting the electron beam of the cathode ray tube in two transversedirections.

8. An electromagnetic yoke for deiiectin-g the electron beam of acathode ray tube comprising, a magnetic core comprising a plurality ofturns of a flat wire having magnetic properties, said wire having amajor dimension lying in a plane transverse to the axis of said core,means for increasing the reluctance of the magnetic flux path of saidcore along the outer surface thereof comprising a nonma-gneticconductive sleeve closely surrounding said core, rand a plurality ofcoils Wound longitudinally along the inner and outer surfaces of saidcore to form a pair of circuits for deecting the beam of the cathode raytube in two transverse directions.

9. A magnetic deiiecting yoke for a cathode ray tube comprising a corecomprising a plurality of closely spaced turns of la ilat metal striphaving magnetic properties, said strip having its major dimension lyingin :a plane transverse to the axis of said core, a non-magneticconductive sleeve surrounding said core, and a plurality of coils woundlongitudinally along the inner and outer surfaces of said core to form apair of circuits for deilecting the beam of the cathode ray tube in twotransverse directions.

RICHARD B. GETHMANN.

